The significance of adenine nucleotide binding sites for the structure and function of mitochondrial ATPase both in hydrolysis and in oxidative phosphorylation will be evaluated. Bound nucleotides will be removed from the enzyme and replaced with isotopically labelled nucleotides or nucleotide analogs and the effect of these substitutions as well as substitutions with a proposed affinity label will be examined. Further investigation into the structure and function of the mitochondrial ATPase, both in solution and when attached to the mitochondrial membrane, will include studies of the interaction of the enzyme with aurovertin and with a peptide inhibitor of the ATPase as well as studies of the enzyme in the oligomycin-sensitive ATPase complex.